I.A. Mkhalid

Synthesis of 2‐ and 2,7‐Functionalized Pyrene Derivatives: An Application of Selective CH Borylation

An efficient synthetic route to 2- and 2,7-substituted pyrenes is described. The regiospecific direct C-H borylation of pyrene with an iridium-based catalyst, prepared in situ by the reaction of [{Ir(μ-OMe)cod}(2)] (cod = 1,5-cyclooctadiene) with 4,4-di-tert-butyl-2,2-bipyridine, gives 2,7-bis(Bpin)pyrene (1) and 2-(Bpin)pyrene (2, pin = OCMe(2)CMe(2)O). From 1, by simple derivatization strategies, we synthesized 2,7-bis(R)-pyrenes with R = BF(3)K (3), Br (4), OH (5), B(OH)(2) (6), and OTf (7). Using these nominally nucleophilic and electrophilic derivatives as coupling partners in Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig cross-coupling reactions, we obtained 2,7-bis(R)-pyrenes with R = (4-CO(2)C(8)H(17))C(6)H(4) (8), Ph (9), C≡CPh (10), C≡C[{4-B(Mes)(2)}C(6)H(4)] (11), C≡CTMS (12), C≡C[(4-NMe(2))C(6)H(4)] (14), C≡CH (15), N(Ph)[(4-OMe)C(6)H(4)] (16), and R = OTf, R = C≡CTMS (13). Lithiation of 4, followed by reaction with CO(2), yielded pyrene-2,7-dicarboxylic acid (17), whilst borylation of 2-tBu-pyrene gave 2-tBu-7-Bpin-pyrene (18) selectively. By similar routes (including Negishi cross-coupling reactions), monosubstituted 2-R-pyrenes with R = BF(3)K (19), Br (20), OH (21), B(OH)(2) (22), [4-B(Mes)(2)]C(6)H(4) (23), B(Mes)(2) (24), OTf (25), C≡CPh (26), C≡CTMS (27), (4-CO(2)Me)C(6)H(4) (28), C≡CH (29), C(3)H(6)CO(2)Me (30), OC(3)H(6)CO(2)Me (31), C(3)H(6)CO(2)H (32), OC(3)H(6)CO(2)H (33), and O(CH(2))(12)Br (34) were obtained from 2. These derivatives are of synthetic and photophysical interest because they contain donor, acceptor, and conjugated substituents. The crystal structures of compounds 4, 5, 7, 12, 18, 19, 21, 23, 26, and 28-31 have also been obtained from single-crystal X-ray diffraction data, revealing a diversity of packing modes, which are described in the Supporting Information. A detailed discussion of the structures of 1 and 2, their polymorphs, solvates, and co-crystals is reported separately.

Optimization of preparation conditions of ZnO–SiO2 xerogel by sol–gel technique for photodegradation of methylene blue dye

The ZnO–SiO2 xerogel photocatalyst was prepared via the sol–gel technique and applied for photodegradation of methylene blue (MB) dye. The optimum conditions for preparation of ZnO–SiO2 gel is 30:70 ZnO:SiO2 molar ratio and TEOS:C2H5OH:H2O:HNO3 is 1:16:12:0.04 molar ratios at 30°C for 30xa0min, at these conditions the photoactivity of ZnO–SiO2 xerogel was 99% at a surface area of 500xa0m2/g after 60xa0min. The optimum loading of ZnO–SiO2 photocatalyst was 0.050xa0wt% that gives 99% MB dye removal efficiency after 40xa0min. The overall kinetics of photodegradation of MB dye using ZnO–SiO2 photocatalyst was found to be of the first order.

Photocatalytic activity of Bi2S3 enlargement by decoration of silver for visible light thiophene degradation

Bi2S3 nanofibers were prepared via a hydrothermal technique and a photoassisted deposition way was applied to prepare silver-decorated Bi2S3 nanocomposites. Bi2S3 nanofibers and silver-decorated Bi2S3 nanocomposites were investigated using many characterization tools such as X-ray diffraction, field-emission scanning electron microscopy, photoluminescence emission spectra, X-ray photoelectron spectroscopy, ultraviolet and visible spectroscopy, and BET surface area. Photocatalytic destruction of thiophene was selected to determine the photocatalytic performance of Bi2S3 nanofibers and silver-decorated Bi2S3 nanocomposites. XRD results confirm the formation of Bi2S3 nanofibers. FSEM results reveal Bi2S3 nanofiber structure and silver was decorated on surface of Bi2S3 nanofibers. XPS results reveal that state of decorated silver is metallic. Decoration of Bi2S3 nanofibers by silver decreases electron–hole recombination rat, decreases bandgap, and increases photocatalytic activity. 0.3 wt% Ag/Bi2S3 photocatalyst has the top photocatalytic activity by which 100% thiophene was degraded within 60xa0min using 1.6xa0g/l photocatalyst dose. 0.3 wt% Ag/Bi2S3 photocatalyst has photocatalytic stability for five times use.